A large uninsured population may have negative effects on the local health care market that extend to those with insurance coverage. The purpose of this project is to determine the relationship between local uninsurance rates and the quality of care provided to Medicare beneficiaries. The theoretical economic foundation for this work is found in models of physician and hospital behavior as well as the industrial organization literature on vertical product differentiation. The analysis will test the primary hypothesis that hospitals and physicians in communities with higher uninsurance rates provide lower quality care to Medicare beneficiaries. Inpatient data on Medicare beneficiaries will be used due to the relative uniformity of their insurance coverage across communities and the inability of individual providers to vary Medicare prices. Quality of care measures will be adapted from the AHRQ quality indicators and additional data on the characteristics of local health care markets will be obtained from a variety of sources. The empirical approach will use the variation in uninsurance rates across local health care markets to identify the effects on quality. Separate models will be estimated for the effects on ambulatory versus inpatient care. The results will contribute to the literature on the community effects of uninsurance as well as to a large scope of work that examines market-level determinants of health care quality. [unreadable] [unreadable] [unreadable] [unreadable]